1. Field of the Invention
This invention relates to novel heterocyclic compounds and to diisocyanates and polymers derived therefrom, and is more particularly concerned with 1,3-alkylene-diazetidinediones, with methods for their preparation, and with diisocyanates and polymers derived therefrom.
2. Description of the Prior Art
The preparation of cyclic and acyclic allophanoyl chlorides and their conversion to isocyanates is known in the art; see, for example, Ulrich et al., J. Organic Chemistry 29, 2401, 1964 and Sayigh et al., ibid p. 3344. U.S. Pat. No. 3,275,618 describes the preparation of cyclic aliphatic allophanoyl chlorides containing up to 4 carbon atoms in the alkylene chain of the ring and the conversion of these allophanoyl chlorides to the corresponding alkylene diisocyanates by heating, optionally in the presence of a tertiary amine scavenger for the hydrogen chloride which is eliminated.
It is also known that organic isocyanates readily form dimers in accordance with the following mechanism: ##STR1## However, the formation of such dimers from aliphatic diisocyanates by intramolecular (as opposed to intermolecular) condensation has not been reported previously nor has the formation of diazetidinediones from cyclic aliphatic allophanoyl chlorides. We have now found that such intramolecular dimers can be obtained from certain cyclic aliphatic allophanoyl halides and that they have valuable properties.